PHOENIX -- More than 280 aging -- and presumably high-polluting -- school buses are going to be replaced, at no cost to Arizona taxpayers.

Gov. Doug Ducey will announce Friday he intends to use more than half of the $59 million the state is getting as its share of a nationwide settlement with Volkswagen to replace buses that are at least 15 years old and have more than 100,000 miles on them.

The available dollars for the buses are going largely to school districts where at least 60 percent of students come from families whose income qualifies them for free or reduced price lunches. The Arizona School for the Deaf and the Blind also will get some new buses.

But Ducey said this allocation formula effectively takes into account more than poverty. He said more than 80 percent of the buses will end up in counties which already are at risk of violating federal air quality standards.

That's why school districts in Maricopa County will end up with 85 of the buses, with 60 for Pima County districts and 30 for Pinal.

The price tag for the buses is an estimated $38 million.

Ducey plans to use the balance of the funds for new large diesel vehicles.

One will be a crew carrier for a newly created Post-Release Fire Crew, made up of mostly of people released from prison who either spent some time on prisoner fire crews while incarcerated or had previous firefighting experience.

And the state will be buying some other heavy equipment, including snow plows, highway sweepers and paint-striper trucks.

What's getting the state all this cash is a decision by Volkswagen in 2016 to settle a nationwide lawsuit over the sale of so-called "clean diesel'' vehicles being marketed under the VW, Audi and Porsche labels that were anything but. It turns out they had a "defeat device,'' programmed to go into a low-emission mode during testing but then spew out pollutants at much higher -- and illegal -- levels when actually on the road.

VW eventually pleaded guilty to three felonies, including defrauding the U.S. Environmental Protection Agency, and agreed to $4.3 billion in penalties and another $4.9 billion to address pollution from the supposedly low-emission diesel vehicles.

Arizona's share of that is $59 million.

But this isn't unrestricted cash. It had to be spent on project to reduce emissions of oxides of nitrogen, the very pollutants that the VW vehicles were spitting out above permissible levels.

The plan being announced Friday still must be approved by the trustee set up by the federal court. That's because the terms of the nationwide settlement with the EPA specifically require that the dollars go toward projects designed to reduce air pollution.

Filings by the state are designed to show that Ducey's plan meets that mandate.

For example, it says that for each school bus replaced, emissions of nitrogen oxides will be reduced by nearly 1.4 tons over that vehicle's anticipated 12-year life.

The governor's office also said it was a conscious decision not to try to replace the aging diesel-powered buses with electric vehicles.

That starts with the fact that fewer than 50 electric school buses could be purchased for the same price as more than 150 conventionally fueled buses. And, by extension, replacing that many diesel-powered buses with new ones results in about 36 percent less pollution than buying fewer zero-emission buses.

Don't look for those old buses to end up being sold off or even given away: The settlement requires that the vehicles being replaced be made inoperable through a hole in the engine block and a cut in the frame.

There were others who had different ideas of how to spend the cash.

For example, Airlines for America, a group that lobbies for the airline industry, asked that the dollars be used to convert ground equipment at airports to all-electric vehicles.

Southwest Gas proposed converting vehicles to use natural gas.

And both the Alliance of Automobile Manufacturers and General Motors suggested having the state erect a network of electric vehicle charging stations, a move that would promote the sale of more electric vehicles, most of which can't go on long trips because of limitations on battery charges.

But gubernatorial policy advisor aide Daniel Ruiz said his boss wanted to use as much of the money as possible to assist K-12 education.

"There are aging school buses in our school districts that need to be replaced,'' he said.

Arizona's share of the national settlement is on top of $40 million VW is paying to charges that it defrauded Arizona residents by selling them vehicles billed as clean-burning diesel.

That deal reached by Attorney General Mark Brnovich provides payments up to $1,000 to each of about 10,000 Arizonans, who bought or leased vehicles manufactured by VW, Audi and Porsche between 2008 to 2015. The money they get will be in addition to anything they have received or will receive from a nationwide lawsuit.

Another $20 million went into the state general fund, with the dollars put into the pool of funds used to increase aid to public education.

Here's the governor's proposed breakdown by county of where the new buses will go: